1. Field of the Invention
This invention relates to communication connector constructions that reduce or compensate for crosstalk.
2. Discussion of the Known Art
Communication connector constructions that suppress or compensate for crosstalk between signal paths carried through the connector, are highly desirable. As defined herein, crosstalk arises when signals conducted or carried over a first path, e.g., a pair of terminal contact wires in a communication connector, are partly coupled electromagnetically into a second signal path, e.g., another pair of terminal contact wires in the same connector. The transferred signals may be detected as xe2x80x9ccrosstalkxe2x80x9d in the second path, and such crosstalk degrades existing signals routed over the second path.
For example, a standard type RJ-45 communication connector typically includes four pairs of contact wires defining four different signal paths. In conventional RJ-45 plug and jack connectors, all four pairs of wires extend closely parallel to one another over the lengths of the connectors. Crosstalk may therefore be induced among different pairs of the contact wires, particularly in mated plug and jack combinations. The amplitude of the crosstalk increases as the coupled signal frequencies or data rates increase.
Applicable standards for rating crosstalk performance of communication connectors, do so in terms of near-end crosstalk or xe2x80x9cNEXTxe2x80x9d. The NEXT ratings are usually specified for mated plug and jack combinations, wherein input terminals of the plug connector are used as a reference plane. Communication links using unshielded twisted pairs (UTP) of copper wire are now expected to support data rates up to not only 100 MHz or industry standard xe2x80x9cCategory 5xe2x80x9d performance, but to meet proposed xe2x80x9cCategory 6xe2x80x9d levels which call for at least 46 dB crosstalk loss at 250 MHz.
Crosstalk compensation circuitry may be provided on or within layers of a printed wire board, to which the terminal contact wires of a communication jack are connected. See U.S. Pat. No. 5,997,358 (Dec. 7, 1999) which is assigned to the assignee of the present application and invention. All relevant portions of the ""358 patent are incorporated by reference.
U.S. Pat. No. 5,547,405 (Aug. 20, 1996) relates to a crosstalk suppressing connector having first and second signal carrying pairs of elongated, laterally spaced contacts mounted in a housing. An intermediate portion of one contact of one pair is formed to overly an intermediate portion of another contact of the other pair, with a dielectric between the overlying portions to provide capacitive coupling between the associated contacts.
U.S. Pat. No. 6,139,371 issued Oct. 31, 2000, and assigned to the assignee of the present application and invention, relates to a communication connector assembly with capacitive crosstalk compensation. The connector assembly features a number of terminal contact wires having free end portions, with contact portions connecting between the free end portions and base portions of the contact wires. At least a first and a second pair of the contact wires have their free end portions extending to define leading portions. One of the leading portions of the first pair of contact wires, and one of the leading portions of the second pair of contact wires, are dimensioned and arranged for capacitively coupling to one another to produce capacitive crosstalk compensation.
If crosstalk compensation is introduced at locations other than at points of electrical contact between mated plug and jack connectors, a resulting phase shift between existing and compensating crosstalk signals may prevent the signals from completely canceling one another. That is, while capacitive crosstalk compensation is desirable since it may be applied over relatively short lengths of the contact wires of a connector, the point at which such compensation is introduced should be as close as possible to the source of offending crosstalk, e.g., a mating plug.
According to the invention, a communication connector includes a connector housing having an opening for receiving a mating connector. At least a first and a second pair of terminal contact wires are supported in the housing, and each pair of contact wires forms a different signal path. The terminal contact wires have base portions, free ends, and generally co-planar intermediate contact portions for establishing points of electrical contact with corresponding terminals of the mating connector. First and second pairs of elongated, parallel capacitor plates are fixed at corresponding free ends of the terminal contact wires. Each pair of capacitor plates are dimensioned and arranged for capacitively coupling an associated terminal contact wire of one pair of contact wires with an associated terminal contact wire of the other pair of contact wires, to produce capacitive crosstalk compensation substantially close to the points of electrical contact between the contact wires and the mating connector. Each pair of capacitor plates extend in a direction substantially parallel to the plane of the contact portions of the terminal contact wires.
In the disclosed embodiment, the first and the second pairs of parallel capacitor plates also extend in a direction perpendicular to the free ends of the terminal contact wires, and are aligned in planes orthogonal to one another.
For a better understanding of the invention, reference is made to the following description taken in conjunction with the accompanying drawing and the appended claims.